the automatic datatype detection was missing for CENTROID functions.
--
Additionally, some JUnit test files of the `adql` package has been moved to
the correct location.

[ADQL] Fix merge side-effects (e.g. '' were not translated any more as a single ' ; NullPointerExceptions when building positions) + transform the test main class for positions into a JUnit test case + Fix some position mistakes.
(note: a tabulation character seems to be interpreted by JavaCC as 8 characters)